1. General Background
The system of the present invention relates generally to an artifical prosthetic foot and ankle combination, and more particularly to a foot/ankle system incorporating dual ankle springs with multi-axial, functional which absorbs, store and releases energy.
2. Field of the Invention
In the field of artifical limbs, and particularly prosthetic ankles and feet, the artifical limbs have been normally constructed as single axis hinging SACH (solid, ankle, cushion heel) foot to the limb along a hinge axis taken through the ankle. It is important to understand that the inter-relationship between the foot and ankle represents various types, and the foot nor the ankle independently can be considered a seperate entity, but rather as an intergral part of the biomechanics of the entire lower limb.
Several patented inventions have addressed the artifical foot and ankle inter-relationship in an effort to seek solutions to proper construction of that system. U.S. Pat. No. 3,754,286 issued to Ryan entitled "Artifical Foot Having Ankle Flexible Mount" sought as its object to provide an artifical limb which would permit flexing of the foot in the vicinity of the ankle along an axis parallel to the sole taken from the toes to the heel of the foot. Accordingly at least one coil spring would be attached to the ankle of the artifical limb in its upper end, and attached to the sole of an artifical foot at its lower end and allowed to flex in columinar flexor therebetween. Therefore, it sought to eliminate the problem of walking on uneven or sloped surfaces without discomfort or injury.
A second patent which is pertinent bearing U.S. Pat. No. 4,442,554 issued to Copes entitled "Bio-Mechanical Ankle Device", sought to rectify poor designs in the ankle/foot relationship such as a solid ankle cushion heel foot or the single axis foot. Citing the advantages and features of the device patented in the U.S. Pat. No. 4,442,554, the inventor felt that his bio-mechanical ankle not only offered controlled subtalar motion, but both plantor and dorsiflexion, and yet was small enough to be used in a below the knee amputation.
The present invention which is designated as the dual ankle springs foot/ankle system is a vast improvement in the development of the multi-axial stored energy prosthetic feet, and addresses serious shortcomings in the present state of the art. Its advantages are that the helical springs which are incorporated into the system are virtually impossible to deflect with normal usage due to the memory factor of the alloy metal. The system has no moving components; for example, cantilevers, ball and socket hinges, universal coupling or 2 way hinge, hydraulic pistons, valves, etc., which may lead to malfunction. The dual ankle springs system has proven beneficial to below knee, knee disarticulation, and above knee amputees. This system provides these patients with maximum energy efficiency and stability. The system can also be used with either an endo- or exo-skeletal prosthesis. If the previous alignment is correct, the D.A.S. foot ankle system may readily be adapted to the amputees present prosthesis. This system is compatible with many standard artifical knee units including some hydraulic ones, as an example, S.N.S. (Swing-N-Stance).
Therefore, a primary advantage of the dual ankle springs system is that it has an ability over previously used prosthetic feet to absorb, store and return all forces generated in the medial-lateral and anterior-posterior axes.
An additional advantage is the ankle spring system acheives maximum energy absorbtion, storage, and return with the rigid carbon fiber foot. The smoothest heel-strike to toe-off gait cycle is obtained with the soft foam foot in combination with the D.A.S. system.
An additional advantage is the use of the system for irregular walking surfaces. The energy absorbed, stored and released during inversion/eversion and plantar/dorsi flexion in the Dual Ankle Spring system is uniformly controlled. This controlled inversion/eversion and plantar/dorsi flexion with energy absorbed, stored and returned action negates jerks, abrupt bumps and inclines which would normally be instantly transmitted from the artifical foot to the stump. The amputee is aided when inversion/eversion and plantar/dorsi flexion occurs because this absorbed, stored, and released energy occurs on the prosthetic side. This allows the amputee to more easily recover his balance with the prosthesis instead of depending solely on the sound limb.
Therefore, it is a primary object of this invention to provide a dual ankle springs foot/ankle system incorporating a multi-axial stored energy prosthetic ankle system so that the amputee may enjoy all outside activities with minimal concern about ramps, inclines, broken sidewalks or any other obstacles that would previously be avoided but now be of little concern due to the unique functioning of the system when worn by the amputee.